Inferring ozone production in an urban atmosphere using measurements of peroxynitric acid
Observations of peroxynitric acid (HOâ NOâ ) obtained simultaneously with those of NO and NOâ provide a sensitive measure of the ozone photochemical production rate. We illustrate this technique for constraining the ozone production rate with observations obtained from the NCAR C-130 aircraft platform during the Megacity Initiative: Local and Global Research Observations (MILAGRO) intensive in Mexico during the spring of 2006. Sensitive and selective measurements of HOâNOâ were made in situ using chemical ionization mass spectrometry (CIMS). Observations were compared to modeled HOâNOâ concentrations obtained from the NASA Langley highly-constrained photochemical time-dependent box model. The median observed-to-calculated ratio of HOâNOâ is 1.18. At NOx levels greater than 15 ppbv, the photochemical box model underpredicts observations with an observed-to-calculated ratio of HOâNOâ of 1.57. As a result, we find that at high NOx, the ozone production rate calculated using measured HOâNOâ is faster than predicted using accepted photochemistry. Inclusion of an additional HOx source from the reaction of excited state NOâ with HâO or reduction in the rate constant of the reaction of OH with NOâ improves the agreement.
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https://n2t.org/ark:/85065/d7dj5gp1
eng
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2016-01-01T00:00:00Z
publication
2009-06-08T00:00:00Z
Copyright Authors 2009. This work is distributed under the Creative Commons Attribution 3.0 License.
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